The invention concerns a clip machine for the dividing and closing of tubular packaging (packaging tube) filled with a stuffing, with at least two axially spaced pairs of radially opposed displacement elements relating to the axis of the packaging tube (tube axis), which are linked and set up with a linear guide, to be compressed radially, linearly towards one another and subsequently in pairs separated axially (expanded) for the local constriction of the filled packaging and the formation of a tubular braid; with a first and then a second sealing tool, which tools are set up to set and close at least one clamp fastener (clip) around the tubing braid that had been formed between the axially separated displacement element pairs, compressed radially towards one another.
Clip machines of this type are known, for example, from DE 196 44 074 C1 (U.S. Pat. No. 6,217,436). Such clip machines are used to close tubular packaging tubes, intestines or artificial intestines—that is, sausages—filled with fluid to thick pasty or also granular (in part) contents.
First, during this process the stuffing is inserted in the packaging (filling), which then is divided into portions by means of the displacement elements (displacing). The displacement elements of each pair have facing V-shaped cutouts, with which they constrict the tubular casing by linear-radial compression and displace the stuffing located in the area being constricted in an axial direction (all directional specifications relate to the tubular axis). Through the subsequent axial separation of the two displacement element pairs an elongated tubular braid is formed to which one or two (in the case of a ‘double clip allocation’) closure elements are applied in the next work cycle by means of appropriate sealing tools.
The first sealing tool (die plate) and the second sealing tool (die), as they are generally known in this category of machine, are driven crosswise to the linear movement of the displacement elements. During the filling and, for the most part, also during the displacement the sealing tools are in their open position, from which they are brought into their closure position, with the clip being formed upon reaching the closure position. After the closing, the closure lever is returned with the sealing tools to their initial or open position.
In the clip machine described at the beginning, clips that are produced from an imprinted aluminum wire strand are typically processed with the clips being bent beforehand into a U-shape and are connected by means of the crosspieces on their limb ends. The strand of clips thus formed is fed along a guide track to the first sealing tool, the die plate, which discharges into the area of the assigned sealing tool.
During the transport of the strand of clips to the die plate, the foremost clip is fed, as is known, by an advancing means that engages intermittently. As long as the foremost clip is still linked to the following strand of clips it is held firmly by it in the die plate. During the closure the die plate is driven into its closure or stroke end position. In this position the foremost clip is pressed against the tubular braid and is clamped between it and the die plate.
At different times, i.e., while the die plate remains in this position, the die moves towards the die plate. Immediately before the clip is closed, the foremost clip is first separated from the following strand of clips by a shearing device provided on the sealing tool. At this moment the foremost clip is free and is pressed against the die plate by the clamping of the tubular braid. Then the clip is deformed by an additional approaching of the die to the die plate, until the sealing tool has approached to the height of the clamp and the clip has been closed around the tubular braid.
During the closure operation the crosspieces of the bent segment of the clip are pressed against the exterior of the clamp limbs and with it are bent around the braid of the packaging material, with the bent segments and crosspiece sections being pressed and compressed bluntly against one another in the process so that a ring, pressed as tight as possible around the braid of the packaging, results.
In specific cases, namely, with relatively stiff packaging material, however, failures may occur, especially when the tubular braid formed by the displacement elements, acting together in pairs, and laid in the still open clamp fastener is pulled a little apart by the displacement elements in the area of the overlap. During the subsequent closure of the clip around the tubular braid, there is a risk then of the packaging material being damaged and/or not being completely encompassed by the closed clip so that the closure is not tight.
This problem is known. For example, in EP 1 140 633 B1 (U.S. Pat. No. 6,675,554) the attempt is made to remedy it by having the tubular braid pressed axially by means of an assigned retention element next to the sealing tool at the level of the clip base before the closing so the braid can not unfurl at the opening of the unclosed clip. However, the processing of different tubular packaging materials and/or tubular cross-sections requires an adjustment of the retention element to the corresponding braid cross-section. A change of tools is not desired because of the potential risk of an incorrect manipulation.
Accordingly, the task of the present invention is to design the closure operation in a simple manner to make it more reliable process-wise.
The task is solved in a clip machine of the type mentioned at the beginning, by having the radial movement direction of the displacement element pairs essentially coincide with the movement direction of the sealing tool.
At the basis of the invention is the knowledge that a principal reason for the unfurling of the tubular braid is in the orientation of the displacement elements, interacting in pairs like shears and overlapping. Promoted by the axial movement apart of the displacement elements and the associated relative movement between the tubular braid and the displacement elements of each pair, the tubular casing material tends to penetrate the gap between the interacting displacement shears. In the process the aforementioned local unfolding or unfurling occurs. Since, in the previously known type of clip machines mentioned at the beginning, the opening/closing movement of the displacement shears, on the one hand, and the movement of the sealing tools, on the other hand, occur orthogonally to one another, the gap of the pairwise, shear-like, overlapping displacement elements was always in the direction of the movement of the sealing tool. Accordingly, the unfolding took place essentially in this direction. The expansion of the braid that had unfurled was consequently larger in the direction of the clip limbs before closing than in the direction perpendicular to it. Precisely this expansion, however, enables the clip limbs to clamp and damage a fold in the braid under the circumstances.
In contrast, the level of the greatest expansion of the braid with the arrangement of the displacement elements or their movement direction as per the invention is cross-wise to the clip limbs of the open clip so that the risk of damage to the packaging wrapping is decreased. Furthermore, the use here of a clip with shorter limbs, in particular, to close a thin braid, would be beneficial, necessitating less compression work during the closing operation, and thus the wear and tear can be reduced.
Besides the advantages mentioned, the mechanism as per the invention has, furthermore, the advantage of reduced spatial dimensions of the elements engaging in the closing because of that same movement direction.
In fact, for example, from DE 101 31 807 C1 (U.S. Pat. No. 6,871,474) a clip machine of another category is known, where the sealing tools and the displacement elements form a kinematically coupled module, which, revolvable around two crank levers, executes a synchronous movement. For that reason, here, too, the movement directions of the displacement elements and the sealing tools coincide. However, what is involved here is a clip machine of another category where, in particular, an expansion movement of the displacement elements is not planned and technically is also not possible. For that reason, no braid free-from-heating can be formed with such a clip machine, which excludes the processing of raw sausage products. Only the machines mentioned at the beginning are provided for these.
The first sealing tool is primarily fastened to an initial (lower) closure lever and mounted and driven by it so that it can pivot.
With this design the strand of clips of the die plate is fed in an advantageous manner along a guide track, which begins in the area of the pivotal axis of the closure lever. This simplifies the feed, since the pivotal axis is fixed in place.
The second sealing tool associated with a linear feed is preferred.
The second sealing tool, the die, can in fact also be fastened to a second (upper) closure lever mounted and driven by it so that it can pivot around the common pivotal axis of both closure levers. A linear back and forth movement of the die, however, improves the kinematics from the perspective of the uniform formation of the clip. This becomes noticeable during the use of different clip sizes, which, depending on the limb length of the unformed clip, causes the opening angle of the two pivotable closure levers to change at the moment of the contact of the die with the clip so that it does not engage simultaneously with both limbs. The result is that an undesired tilting or torsional moment occurs.
If, on the other hand, the movement of the second sealing tool is executed linearly, preferentially perpendicular to an intended connecting line of the limb ends of a clip laid in the first sealing tool (the die plate), the source of the error described is avoided, since the angle position of the sealing tools to one another no longer changes after the first swivel movement of the lower sealing tool.
In an advantageous further development, the clip machine demonstrates a control that is set up to drive the sealing tools, overlapping time-wise with the radial feed movement and/or the axial separation movement of the displacement element pairs, towards one another radially.
Since the facing V-shaped cutouts of the displacement elements demonstrate preferentially opening angles that are less than 90°, their opening cross-section in the movement direction is greater than perpendicular, too. Since, as per the invention, the movement direction of the sealing tools coincides with that of the displacement elements, a greater adjustment range of the sealing tools is required in order to release the opening cross-section completely. The loss in time associated with the greater adjustment range can at least be partially compensated for, on the one hand, by the temporal overlapping of the movements of the displacement elements and, on the other hand, of the sealing tools. In this movement section the sealing tools can follow maximally the total travel of the feed movement of the displacement element pairs. Timewise, the control can see to it that the sealing tools follow the displacement elements during the compression synchronously with the same speed. In principle, the entire interval of the radial feed movement and the axial separation movement of the displacement element pairs can be used for the subsequent movement.